The present invention relates to a process for the preparation of ethyltrifluoroacetoacetate and, more particularly, to a process for the preparation of ethyltrifluoroacetoacetate by condensation of ethyltrifluoroacetate and ethyl acetate in the presence of a base.
The condensation of ethyltrifluoroacetate and ethyl acetate in the presence of sodium ethoxide is known, as discussed in Swarts 5 Bulletin des Sciences academiques du Royaume de Beliqique (12) 679-725 (1926). The condensation is carried out by refluxing in an anhydrous ether medium and leads to sodium enolate. The enol, which is released with sulfuric acid, comes to equilibrium with its ketonic form. This reaction in a aqueous medium and in the presence of a strong acid results in a partial hydrolysis of the .beta.-ketoester, which severely reduces the profitability of the process.
It is also known, according to Bayer, Pastor, and Cambon 20 Journal of Fluorine Chemistry (1982), to perform the same process as above, but with the sodium ethoxide being replaced by sodium hydride. Although the yields obtained are greater, like the previous process, the use of ether in large quantities and the neutralization with an aqueous mineral acid render this process difficult to use from an industrial point of view because of the need for indispensible safety measures coupled with the low economic profitability.
Some authors, such as Burdon and MacLoughlin 20 Tetrahedron 2163-66 (1964), have tried to avoid the use of ether during the condensation of the ethyl esters of trifluoroacetic and acetic acids. However, the phase of enol release is always carried out in an aqueous medium with the use of ether and, hence, these processes cannot be applied on a large scale.
Quite a different reaction technique is described in French Pat. No. 1,310,174. This patent describes the condensation of trifluoroacetic acid chloride with CH.sub.2 =C =O followed by an esterification with ethanol. The condensation is carried out at a very low temperature, such as -30.degree. C., in a dichloroethylenebased medium. The trifluoroacetic acid chloride is a gas with a very low boiling point. It is difficult to obtain for industrial use and it is toxic. The ketene CH.sub.2 =C=O is also dangerous to use because it is unstable and difficult to transport. Therefore, this process can hardly be considered usable in industry.